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Subject: FAQ:PdoxWin:Net File Rules:2000.01.18

Version 1.0 (2000.01.18)
edited by Paradox FAQ Team
Reposted by Mike Irwin: 2001.02.10

====================
0. Introduction
====================
This FAQ addresses the rules to abide by when setting
up a location for a .NET file for Paradox.

-------------------------------
 0.1 Legal Info and Disclaimers
-------------------------------
Paradox is a trademark of Corel.
Borland Database Engine (BDE) is a trademark of Inprise.
The information provided in this FAQ is provided "as is" 
and
is not warranted in any way. The information provided in
this FAQ is not endorsed or authorized by Corel or Inprise
in any shape, form, or manner. The editors claim NO
responsibility for ANY illegal activity regarding this 
file,
or as a result of someone reading this file.
You may distribute this file, as long as the copies are
complete, unaltered, and are in electronic form only.
-------------
 0.2 Feedback
-------------
Please send feedback in a Corel Paradox newsgroup or the
news:comp.databases.Paradox newsgroup to any of the FAQ
Team mentioned in the "FAQ: FAQ FAQ" document.
Please preface the subject of your post with the string
"PDXWIN FAQ" to alert Team members to the function of
the message.
Please specify the FAQ name and section number the
comment applies to, if any.

==============================
1. General Information
==============================
Paradox is a client and file based database system. This 
means that each user has one or more instances of the 
client (the Paradox program) running on his or her machine. 
No copies of Paradox need be loaded or running on any 
central server machine, even if the use of a central data 
server is part of your design.

Each machine running Paradox also loads an instance of the 
Borland Database Engine, the BDE. This piece of software is 
responsible for providing the interface between the part of 
Paradox that you see and the tables and files that store 
the data. It's for this reason that we concentrate here on 
what the BDE does and offers, rather than what Paradox 
offers, which is largely dependent on the BDE.

There can only be one instance of the BDE running on a 
particular machine at any one time. You can have any number 
of instances of Paradox, for example,  running 
simultaneously, but they will all use the same instance of
the BDE.

At load time the BDE will read a configuration file. This 
may be specified by the user if you are running Paradox 
(see the "-o" command line switch).

Amongst  other things, this file will define a directory 
called the "Net Directory". This directory is a common 
location visible to all instances of the BDE that wish
to share Paradox files. In this directory a PDOXUSRS.NET 
file will exist to record the active instances of the BDE. 
It is possible to delete this file safely when no instances 
of the BDE are connected to it. The first time an instance
of the BDE loads it will re-create the file if it does not 
already exist.

The BDE offers a number of types of locking for Paradox 
tables, including "read locking", "write locking", and 
"exclusive locking" on tables (see the Help topic "Locking 
Tables"), and the locking of individual records within a
table for the purposes of editing. Whenever any such locks 
are requested a .LCK file is created or updated within the 
directory that contains the table involved, and reference 
is made to the .NET file in order to facilitate 
coordination beteewn instances of the BDE.

Note here that it is perfectly possible to have two 
entirely independent sets of instances of the BDE on one 
network, each set with its own .NET file. So long as no 
member of one set is used to access tables in use by a 
member of the other set, nothing untoward will occur. 
However, as soon as sharing is required, all the users of a 
particular Paradox table must also share the same .NET 
file.

==============================
2. The Rules
==============================

The following are, we believe, the minimum necessary and 
sufficient set of rules to observe in order to achieve an 
operating set of instances of the BDE on a network where 
Paradox tables must be shared.

2.1    For each instance of the BDE cooperating on a 
network there must be a Path Specification to the directory 
to hold the PdoxUsrs.Net file.

2.2    The path specification shall be composed of a Drive 
Letter and a Path String

2.3    The Path String must be identical in form (but not 
necessarily in case) for each and every instance

2.4    The Drive Letter is not restricted in value or case 
at all 

2.5    There are only 4 Rules

There are ONLY 4 rules !!!! Forget all about the  
Paradox.net and Paradox.lck files; they'll have little or 
nothing to do with you unless you have a system
crash.

=============================
3. Recovery
==============================

If you are unlucky enough to have a system crash the steps 
to follow before continuing are:

1. Make all users stop using all copies of Paradox, and 
remain thus until you have finished.

2. Check all tables for integrity. One recommendation is to 
have a set of empty copies of all your tables available and 
a script that exports all the data from your full tables 
into text files and then puts it back into a set of empty
tables again. Remember that, with relational integrity and 
lookups, the order in which you fill tables does matter ! 
Most times you will not need this, but on the occasion
that you do you will be very grateful for a little 
planning.

3. Delete all .lck and .net files on all machines with 
Paradox installed and on all machines where Paradox 
accesses tables (shared network machines, for
example).

4. On every machine check the BDE configuration (if each 
machine has its own) to ensure that all point to the same 
Net Directory.

5. Resume operations.

6. Make another backup.

7. Once things are going well again, find out what caused 
the crash and eliminate the cause.


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